Drugs, vaccinations, and other medical materials that are to be delivered to tissue that is covered by skin are typically injected using a hypodermic needle. Similarly, tattoos and permanent makeup are also typically applied using needles that penetrate the skin surface.
Although the use of needles for transcutaneous or subsurface delivery is well established, being very robust and reliable, there are some disadvantages to the use of needles. For example, reuse of needles may be a common practice in regions or circumstances where an adequate supply of needles cannot be relied upon. Such reuse of a needle after inadequate sterilization could lead to infection or spread of disease agents from person to person. Some people are frightened by the sight of the needle and by the realization that the needle is to penetrate their skin. Insertion of the needle is an invasive procedure which could be painful, cause bleeding, or otherwise traumatize tissue to some extent. In some cases, momentary inattention to an exposed needle may result in accidental pricking of medical personnel or of bystanders, possibly resulting in injury or infection.
Needleless transcutaneous or subsurface delivery may require a smaller amount of the delivered liquid than delivery via a needle. Reducing the amount of the delivered liquid may reduce the probability of skin irritation or an allergic reaction.